How can we improve Excel for Mac?

Allow switching between Light or Dark theme in Excel.

With the new Mohave MacOS update, the dark theme setting has become global which now impacts MS Excel for mac. With the dark theme turned on the colour scheme on excel looks horrible and is very harsh on the eye because of massively contrasting colours. See ribbon screenshot attached, the colours stand out. If you have a sheet which has been colour coded to explain things, visually the sheet stands out and is very harsh on the eyes.

There should be an option within Excel to switch back to the "Light" theme, but for people who like the dark theme, they should be allowed to keep it as is. So the option to switch between Light/Dark is what is required.